Method for filling abandoned mines



United States Patent 3,478,520 METHOD FOR FILLING ABANDONED MINES AlbertAndy, Washington, Pa., assignor of one-fourth each to Anthony Andy,William Andy, and Victor Andy, all of Washington, Pa. No Drawing. FiledNov. 16, 1967, Ser. No. 683,482 Int. Cl. E02d 27/32; E21f 15/.00

US. Cl. 61-35 3 Claims ABSTRACT OF THE DISCLOSURE This invention relatesto a method for filling abandoned mines or mine cavities with a materialwhich will completely fill such mines or mine cavities as the result ofapplication of heat to the material when located in the mine so as toserve also as a strong mechanical reinforcement for the roofs of themines and cavities.

In the past, various methods have been used for partially filling orreinforcing abandoned mines and mine cavities, such as the erection ofposts or pillars to support mine roofs and the introduction of concrete,a rather expensive material, to form such pillars to partially fill suchcavities and adequately support the ground thereabove to preventsubsidence. While these methods have been at least partially successful,they have not provided a complete filling of the voids or cavities andtherefore have permitted an objectionable amount of subsidence orwithdrawal of support of foundations for homes and other structuresresulting in cracking the walls and sinking of foundations, causingconsiderable expense for reconstruction without assurance that thesubsidence will not recur.

An outstanding disadvantage of such methods has been not only theineffectiveness in preventing subsidence but the very high cost involvedin the use of concrete that is, lime, sand and gravel, since minesinvolve very large volumes of air space that must be filled.

An object of my invention is to overcome the above named disadvantagesof presently used methods for reinforcement of mine roofs or forpartially filling mine cavities.

A further object of the invention is to provide a comparativelyinexpensive method for completely filling mine cavities and at the sametime providing a very strong mechanical support for the roofs or groundstructure above so as to eliminate any possibility of subsidence.

Another specific object of the invention is to introduce, into minecavities, a granular material which will expand many fold as aconsequence of the application of heat, such as an expandablepolystyrene, so as to completely fill an abandoned mine and its variouscavities with a minimum of effort and expense, as well as a minimumamount of time, so as to make such method very inexpensive and thereforehighly practical.

In accordance with the present invention, a material is used which willhave the characteristics of expanding many fold when placed in a minecavity or any other cavity in the ground, also which will have adequatestructural strength when expanded to support mine roofs or layers orstrata of coal or earth thereabove to avoid the possibility ofsubsidence of structures built on the ground surface. I have found thatexpandable polystyrene ice has this unique quality, as well as theadditional unknown characteristic of not being subject to deterioration,after expansion in ground cavities, by mine acid, water streams and thelike which are usually present.

However, in order to expand such polystyrene, it is necessary to apply apredetermined amount of heat in order to initiate expansion and tocontinue such expansion until the volume of polystyrene expands manyfold. Various ways may be employed for introducing such heat into minecavities. For example, steam heated pipes may be introduced throughhollow shafts sunk through the top layers above the mine cavities, withheating coils extending into or immediately adjacent the granularexpandable material in the mine cavities so as to apply the necessaryheat to initiate expansion of the polystyrene.-

Instead of steam, propane gas may be introduced to supply a burneradjacent the granular expandable material in the mine cavity. Stillanother means is an electric heating coil which is energized by a supplyline introduced in a similar manner as the steam pipes, which coil isplaced immediately adjacent the polystyrene to apply sufiicient heat forcomplete expansion thereof to enable the filling of mine cavities andvoids. The expandable polystyrene is preferably of a granular sizeslightly greater than that of sugar.

In some instances, exothermic materials may be mixed with thepolystyrene particles, such as those used in exothermic sideboards foringot molds to prevent piping, which exothermic materials can be ignitedso as to give off heat by the application of a predetermined ignitingtemperature. Such exothermic materials are well known in the art,therefore, any of such materials may be mixed with the expandablepolystyrene particles so as to generate or give 01f a certain amount ofheat after a predetermined temperature or heat has been applied thereto,such as by the methods described above. In short, any used for thepurpose of initiating expansion of the exmethod of introducing heat intothe mine cavities may be used for the purpose of initiating expansion ofthe expandable polystyrene or equivalent material.

Unusual and unexpected characteristics of the polystyrene when inexpanded condition are the remarkable and amazing structural strengthwhich provides very strong support for the roof of the mined areas anduniform distribution of the roof load throughout the entire area that ismined so as to prevent any concentration of loading on any one singlepillar or several pillars, such as used in the past, which are subjectto failure in spite of the very high expense involved in theconstruction of such pillars, or in the wasteful leaving of unminedpillars solely to serve as supports.

Still another unusual characteristic providing unexpected results by theexpanded polystyrene is its great resistance to mine acid drainage or tounderground streams, as well as to air and moisture, that is,its-stability or.tendency not to disintegrate as a consequence ofcontinual exposure to mine acid, underground streams dampness, etc.

While I have described granular, expandable polystyrene as a verysuitable material to accomplish the purposes of the present invention,it should be understood that others, after having had the benefit of thepresent disclosure, may select other full chemical equivalents, that is,materials which can be expanded by the application of heat, to provide asimilar cellular structure with similar characteristics. Instead ofapplying heat to initiate expansion, other known means may be usedinstead, such as the use of catalysts, exothermic materials or the liketo initiate and to continue expansion until complete filling of themines or mine cavities has been accomplished.

Thus it will be seen that I have provided a highly efficient andeifective method for filling abandoned mines and mine cavities, whichmethod can be accomplished more quickly and inexpensively thanheretofore possible so as to make it practical, for the first time, tocompletely fill all voids of mine cavities and thus provide suflicientstructural support to prevent subsidence, as well as to completely fillthe voids and thus prevent introduction of underground streams whichcould become polluted with acids as a consequence of infiltration in themines cavities.

I claim: I

1. The method of filling mines and underground cavities in a manner soas to adequately reinforce the ground thereabove in order to preventsubsidence, comprising introducing into said mines and cavitiesparticles of expandable plastic material having the property ofexpanding many fold upon the application of heat and having highstructural strength and resistance to mine acid drainage, moisture andair, sinking, through the ground surface above said mines and cavities,supply lines for applying heat in contiguous relationship to saidparticles of expandable plastic material sufficiently to initiate andcon- References Cited UNITED STATES PATENTS 3,294,602 12/ 1966 Franciset al. 264-45 X 3,311,575 3/1967 Graham 260-25 3,320,188 5/1967 Dijkema26025 3,340,693 12/1967 Row 61-36 3,388,195 6/1968 Christenson 264-45JACOB SHAPIRO, Primary Examiner US. Cl. X.R.

